Highly luminescent semiconductor nanocrystals, usually referred to as quantum dots (QDs) with their unique size/composition-tunable narrow emission and broad absorption spectra have drawn great attention in the last decade due to their promising application in optoelectronics and biology. In particular, nanoparticles functionalized with various chemical groups have found many applications in sensing, nanofabrication and biolabeling, among others. For many of these applications the quantum dots have to be soluble in water.
Hydrophobic quantum dots can be solubilised in water either by exchanging hydrophobic TOPO ligands at the quantum dot surface with hydrophilic ligands or by using amphiphilic polymers, which can have both hydrophobic-hydrophobic interaction with hydrophobic ligands on the surface of quantum dots and hydrophilic interaction with water molecules in the medium. The use of amphiphilic polymers has some important advantages over the ligand exchange approach such as the omission of the ligand exchange step and the easy introduction of functionality without affecting the surface of the quantum dots, which could result in deterioration of their optical properties.
Recently, a family of amphiphilic polymers which allows solubilisation and easy functionalization of TOPO-terminated quantum dots has been synthesized and characterized. It allows the transformation of hydrophobic quantum dots into hydrophilic quantum dots for various bio-applications. This family of amphiphilic polymers allows convenient control of the type and number of hydrophobic units in the backbone chain and to optimize polymers to provide water-soluble quantum dots, as well as to easily functionalize the quantum dots without the use of coupling agents. The multi-point hydrophobic attachment of polymers to the hydrophobic layer on quantum dots provides sufficient shell stability in water for an extended period of time without cross-linking.
The amphiphilic polymeric material is synthesized by grafting different side chains with nucleophilic character into a polymeric backbone containing repeating anhydride unit. Upon anhydride ring opening one obtains amphiphilic chain with pendant (both) carboxylic and alkyl chains. As shown in FIG. 1, a series of amphiphilic polymers were synthesised by grafting n-octylamine to poly(isobutylene-alt-maleic anhydride) at different molar ratios. The grafted alkyl chains (like for example n-octylamine chain) have hydrophobic character and serve as anchoring points for attachment to the TOPO terminated quantum dot surface.
There is, however, still a need for more sophisticated water-soluble nano-particles or nanoparticle composites, in particular for use in sensing or nanofabrication.
Accordingly it is an object of the present invention to provide water-soluble nanoparticles that are suitable for sensing and/or immobilization, ideally including 2D and 3D patterning. This object is solved by providing an amphiphilic polymer according to claim 1.